We propose to investigate the use of artificial lipid bilayer particles, liposomes, as vectors for introducing biologically active materials into tumor cells. Liposomes are prepared from various purified and chemically defined lipids, phospholipids and cholesterol, or from the lipids extracted from autologous organs or cells of the host. In addition, we prepare glycoproteins and glycolipids from various target tissues, such as lung, mammary, liver, and prostate carcinoma. These preparations are incorporated into the liposomes and tested for efficiency of fusion peferentially with the desirable target organs and with the malignant cells. Various chemotheraeutic agents such as methotrexate, Ara-C, adriamycin, 5FU or new agents are encapsulated and tested for the efficiency in delivering them with liposomes. In addition, liposomes containing the active phosphorylated forms of antimetabolites are used in efforts to circumvent drug resistance resulting from diminished rates of intracellular phosphorylation. The results of this study may contribute to the development of improved therapeutic approaches and to the possible solution of drug resistance in neoplasia.